(a) detecting in the secondary winding voltage zero crossings occurring unequal amounts of time apart by an amount related to the amount of current being supplied by the secondary winding;

(b) adjusting an indication of the zero crossings detected in step (a) to have equal periods of time between successive indications of zero crossings while retaining the same frequency as the secondary winding voltage;

(c) detecting in a different winding of the power transformer voltage zero crossings occurring unequal amounts of time apart by an amount related to the amount of current being supplied by the secondary winding;

(d) adjusting the an indication of the zero crossings detected in step (c) to have equal periods of time between successive indications of zero crossings while retaining the same frequency as the voltage of the different winding;

(e) amplifying the voltage drop across a series regulation element whose input is supplied by a filter capacitor and whose regulated output voltage is applied to a load, the amplification having a transfer function that describes as a comparison voltage a location in phase when to begin charging the filter capacitor from a rectified half-cycle of a sinusoid voltage from the secondary winding to keep the voltage drop approximately constant;

(f) creating a reference ramp waveform of constant amplitude representing with each cycle thereof the duration in phase of a rectified half cycle of the secondary winding voltage, and having one such cycle for each adjusted indication of step (d);

(g) comparing the comparison voltage of step (e) with the reference ramp of step (f);

(h) connecting the rectified secondary voltage to the filter capacitor upon a selected comparison in step (g); and

(i) subsequent to step (h), disconnecting the rectified secondary voltage from the filter capacitor upon the occurrence of an adjusted zero crossing indication of step (b).